This invention relates to rolling doors and in particular operating systems for opening and closing doors of this type.
The use of rolling doors, particularly for industrial applications and for mining, is well known. These doors can be of various constructions including flexible doors made from rubber or plastic sheets. The door is rolled up about a horizontal shaft extending across the top of the door opening. There can be a spring loaded barrel arranged on the shaft about which the door is rolled. The purpose of this barrel is to overcome the gravitational forces acting on the door so that the door will open with relative ease. It is common to provide an electric operator including an electric motor to open and close the door. Vertical guideways are generally provided along the sides of the doorway to accommodate the edges of the flexible door.
In U.S. Pat. No. 4,478,268 issued Oct. 23, 1984 to Copper Cliff Door Manufacturing (1980) Ltd., there is described a roll-up door made from a strong rubber curtain. Since the curtain is of rubber, if it is struck by a vehicle accidently it will give with the force and, unless it is hit with considerable speed, it will be substantially undamaged. With this door it is generally a simple operation to reinsert the rubber curtain back into its vertical guide channels and make the door operational again. A motor and clutch is provided to open the door. A chain drive extends from the clutch to the shaft about which the door is rolled. A worm and screw arrangement is provided between the drive shaft of the motor and the clutch.
Although the door of the above-mentioned United States patent has been found to be generally satisfactory, difficulties have been encountered with the closing of such doors when there is a pressure differential between one side of the door and the other. This situation is encountered most frequently in mining situations. Often a section of the mine must be kept under pressure in order to maintain the mine in an operational and safe condition. Where a pressure differential exists, the friction between the vertical edges of the rolling door and the guideways can build up to such an extent that the door will not close satisfactorily.
U.S. Pat. No. 2,819,628 issued Jan. 14, 1958 to Coolsson Company describes a control device for a rolling door that includes a power operated mechanism and a hand chain mechanism for controlling the door. The main shaft is adapted to be rotated by either the power operated mechanism or the hand chain mechanism. The latter consists of a hand chain loop which has one end looped about and engaging a chain sprocket. The chain is of sufficient length that it can be reached by a person standing on the floor. A spur gear is adapted to be moved into meshing engagement with either of two pinions by means of a Scotch yoke mechanism. If it is desired to raise or lower the curtain by the motor, an operating rod is pulled to its lowermost position, which operation serves to urge the yoke downwardly. This results in the spur gear moving into engagement with the pinion that is driven by the motor. There is no means provided in the device of this patent for pulling the flexible curtain downwardly in its guideways.
More recent U.S. Pat. No. 3,853,167 issued Dec. 10, 1974 to The Cookson Company describes a driving mechanism for a rolling door that includes a motor driven gear box which is selectively coupled by an electro-mechanical clutch and a manual operating mechanism. A safety brake coupled between the clutch and manual operator prevents driving of the manual operator by the motor should the clutch fail to disengage and functions as a stopping brake whenever the motor is stopped. In this known device a main drive sprocket is mounted on the end of the axle of the curtain barrel. The main drive sprocket is connected by means of a drive chain to a smaller sprocket mounted on the output drive shaft of the gear box.
It is an object of the present invention to provide an operator for a rolling door which provides both a power operated means for rolling the door up and a means for pulling the door downwards to the closing position under power. Thus, a rolling door provided with the operator of this invention can be used in at least a medium pressure environment such as the type found in many mines.